I've been studying a thing like this for my Leopard Geckos and every plan poses a problem, either in safety or in hygiene.
Fixed, rigid structures are great for their safety but lousy for hygiene. They can be also a nightmare if one of them hides in a secluded place where you can't get to.
Piled up, assemblable structures are great to clean and to "fine tune" them to their needs but pose a serious danger if they collapse.
My best solution so far is to use a modified wine rack. They are designed to stand a lot of weight and you have so many different types, you can choose the one that fits best your current enclosure decoration, from a simpler one like
this to a more
sophisticated type.